In a country where demonstrations often end with masked teens hurling steel bars or riot cops spraying down neighborhoods with tear gas, a protest during yesterday’s presidential election was notable for its silence.

In elections that sent former President Michelle Bachelet and former labor minister Evelyn Matthei to a runoff, about 8 percent of voters quietly wrote “AC” on their paper ballot, adding their voices to a nationwide call for a constitutional assembly to replace the country’s dictatorship-era political system.

How the Constitution might be changed proved a hot topic during the election campaign. Supporters of a constitutional congress, for which there is no provision in Chilean law, say their campaign succeeded even if it did not persuade many to spoil their ballots.

“We got this onto the table for discussion,” says Maritza Canobra, who worked on the campaign. “We got the support of seven parties and some of the campaigns.... No one has ever called for direct action like this before.”

The non-binding demonstration of support for a constitutional assembly could add pressure on the next president to allow a broader public role in forging promised constitutional reforms. But there are those on both the right and the left of the political spectrum who are wary of populism and of hasty change.

The AC (for Asamblea Constituyente) campaign was one of the few surprises left in an election whose results had largely been forecast for months. Ms. Bachelet won 47 percent of the vote, missing the absolute majority she needed to avoid a runoff. She is apparently comfortably placed to beat her conservative rival Evelyn Mattei, who won 25 percent, in a runoff election on Dec. 15.

During the campaign, Bachelet promised a “new constitution” but said she would create it using the existing institutional system. Unlike the United States, the Chilean charter has no mechanism for calling a constitutional convention.

The main text of the current Constitution was imposed by Gen. Augusto Pinochet in a plebiscite dominated by the military dictatorship in 1980. The document has been changed several times, with President Ricardo Lagos – a left-leaning post-dictatorship president – so happy with the changes that he replaced Pinochet’s signature on the document with his own. But Chileans remain dissatisfied with the government structure.

But even some who support constitutional change didn’t join the AC movement. One skeptic is Jorge Caravantes, who says the country needs a new legislative system and more rights for people, rather than corporations. But he isn’t convinced that a constitutional assembly is the way to go.

An assembly will invite “a populist system like Venezuela,” he says. “That would be a worst case, and I don’t want a worst case.”

Robert Funk, a political scientist at The University of Chile, agrees.

“It shares characteristics with two things I don't like: populism and revolutions,” he says. “The argument is, the ends justify the means. We need a new constitution, and since current institutions don't allow it, you go outside the institutions. That's revolutionary.”

Mr. Funk warns that such a breakdown in institutions could soon encourage powerful political figures to ignore the Constitution in order to impose their policy.

Funk says Bachelet’s platform offers a better, if cautious, route to reform. She wants to change the electoral rules that overrepresent conservatives. Elect a new legislature. And years down the road, make constitutional changes through the process outlined in the 1980 Constitution.

“The argument is that that is too slow,” Funk says. And protestors, already distrustful of Bachelet, may have little patience for such measures. “If [the new government] doesn't show results in six months they'll have students on the streets,” he says.

And it’s already started. During the election, 20 students briefly took over Bachelet’s campaign headquarters to demand constitutional changes.